The present invention relates to a database management system, more specifically, to a technique suitably applied to an object-oriented database management system.
It should be noted that the present invention is related to the co-pending U.S. pat. application Ser. No. 08/038, 634, entitled "OBJECT MANAGEMENT SYSTEM" filed by T. Maruyama et al., on Mar. 29, 1993, now pat. no. 5,526,519.
In the conventional object-oriented database management system, an object corresponds to a data set containing an object identifier for exclusively indicating the object, a length of the object, the attribute number, attribute information, attribute data, and an offset for storing attribute data.
As to the above-described technique, Wom Kim; "Introduction to Object-Oriented Database", The MIT press, 1992, pages 107 to 114 describes such an object, class, instance and clustering.
Then, in the conventional object-oriented database management system, the database is subdivided into several physical regions called as "partitions", a plurality of segments each containing several storage regions referred to "pages" are formed on each of these partitions, and such objects under one relationship are stored in one of these storage regions for management purpose, paying attention to a plurality of objects having a common attribute, a plurality of objects belonging to the different class and having the common attribute, or a part of an object.
Normally, an object having either the common attribute, or a dependent attribute with respect to the data about one attribute of the object, the attribute defining one character of the object, stored in the same storage region can be read out with one accessing operation together with the one attribute, giving a merit in performance.
The Applicants of the present invention could find out the following problems by investigating the above-described prior art.
That is, the above-mentioned prior art does not consider to obtain data of one or a plurality of selected common attributes among a plurality of objects within one time. In order to acquire the data with one attribute of the plural objects within one time, all of these plural objects arranged at the physically adjacent locations are first acquired, and then the attribute data should be selected in accordance with the offset of the attribute data and the attribute information owned by the object.